Thermostatic disk



Dec. 21 1927. 1,654,519

L. J. GREENAWALT THERMOSTATIC DISK Filed Feb. 1, 1927 WIT ESSES: INVENTOR 2? (39 L ew/s J fireenawa/f Patented Dec. 27, 1927.

UNITED STATES PATENT OFFlCE.

LEWIS T. GREENAWALT. OF MANSFIELD, OHIO, ASSIGNOR TO WESTINGHOUSE ELEC- TRIC & MANUFACTURING- COMPANY, A CORPORATION OF PENNSYLVANIA.

THERMOSTATIO DISK.

Application filed February 1, 1927. Serial No. 165,105.

My invention relates to thermostatic devices and particularly to bimetallic disks therefor.

An object of my invention is to provide a thermo-resp onsive bimetallic disk so constructed that itmay be actuated from an initially curved position to a position of reverse curvature without subjecting the disk to severe internal stresses.

In practicing my invention, I provide a bimetallic disk having a spherically or nondevelopable curved surface the curvature of which is reversed by subjecting the disk to a temperature of a predetermined value.

In order to reduce the stresses in the disk incident to reversing its curvature, a plurality of sections are removed from the disk whereby portions are provided that extend radially trom a peripheral portion towards the center thereof. These portions are sepa-- rated from each other at the center of the disk in order that the respective ends thereof may move independently of each other.

In the single sheet of drawings, Fig. 1 is a top plan view of a thermostatic switch embodying my invention;

Fig. 2 is a View in side elevation, partly in seciion of the device illustrated in Fig. 1; an

Fig. 3 is a top plan view of a bimetallic disk embodied in the device illustrated in Figs. 1 and 2.

In the drawings, a thermostatic switch 11 comprises a base 12, a disk of insulating material 13 disposed between the base 12 and a plurality of stationary contact plates 14, 15, 16 and 17, of arcuate shape, and a bimetallic disk 18 that is attached to the base 12 by means of a screw-threaded stud 19.

Th stationary contact members 14 and 15 are secured to the base 12 by means of terminal bolts 21 and 22, the heads of which are peened over against the contact members. The contact members 16 and 17 are suitably secured to the base 12 by such means as rivets 23, the heads of which may be peened or spun over against the contact members and the base 12. The terminal bolts 21 and 22 and the rivets 23 are suitably insulated from the base 12.

The bimetallic disk 18 is of the type, disclosed and claimed in the Patent #1, t-18,24O issued to J. A. Spencer, having a spherically curved or non-developable portion so that it may be actuated from one position to another with a snap motion by a reversal of its curvature. The reversal of curvature of the spherically curved portion 01' the disk is caused by the unequal expansion of the metals of which it is composed.

A plurality of portions of the disk 18 are so cut away (see Figs. 1 and 3) that a plurality of radial portions or spokes 21 are pro vided which extend from an annular rim portion 25 towards the center of the disk. The portions 2st are severed at the ends terminating at the center of the disk in order to permit free movement thereof. The inner ends of the, portion 24. are arcuatc in shape in order that the disk 18 may be mounted on the stud 19 and be operatively secured thereto by such means as a nut 26. A suitable clearance is provided between the nut 26 and a shoulder portion (not shown) on the stud 19 whereby the ends of portion 24 may move longitudinally along the stud 19.

A plurality of movable contact members 26a are secured to the periphery or the rim portion of the disk 18 by means of washers 27 and pins 28. The ends of the pins 28 are spun over against the washers 27 and the contact members 26a in order to maintain the contact members in operative relation to the disk 18. W'ashers 29 of electric-insulating material are disposed between the disk 18 and the washers 27, thereby insulating the pins 28 and-the contact members 26 carried thereby from the disk 18.

The contact-bridging members 26 are so spaced along the rim portion of the disk that they engage the adjacent ends of the contact members 14, 15, 16 and 17, thus pr0- viding a cuwent-conducting path between the terminal bolts 21 and 22. A turning movement of the disk 18 on the stud 19 is prevented by a pin 31 secured in the base 12 and extending through the disk 18 near the periphery thereof.

\Vhen the disk 18 is heated to a predetermined temperature, its curvature is suddenly reversed, thus causing the contact members 26 to be moved out of engagement with the stationary contact members 14, 15, 16 and 17 with a snap motion. The currentconducting path between the terminals 21 and 22 is, therefore, interrupted.

The stresses resulting from reversing the curvature of the disk, as illustrated in Fig. 2 of the drawings, is materially reduced by reason of the fact that the spokes or portions 24 (see Fig. 8) may yield or deflect during the reversal of curvature of the rim portion of the disk. The strains in the disk are materially reduced also because the body of metal, of which resistance to bending must be overcome in order to reverse the curvature of the disk is grcatl diminished.

\Vhile I have made no mat ematical analysis of the reduction in stresses obtained by ren'ioving portions of the disk 18, as illustrated in the drawings, I have found by experiment that a disk constructed in this manner will operate an indefinite number of times and still maintain its resiliency. The fact that the disk still maintains its resiliency after a large number of reversals of curvature is evidence that the strains are greatly reduced.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof. I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. A thern'io-responsive means for actuating the Contact members of an electric switch with a snap motion, said means comprising a bimetallic disk having a spherically curved surface, said disk being perforated to provide a plurality of spokes, the ends of which are free to move at the central portion of the disk.

2. A thermostatic disk comprising a bimetallic member having an outer portion and a plurality of spaced portions extending radially towards the center of the disk, said spaced portions being disconnected at their inner ends.

3. A bimetallic disk having an initial deforn'iation therein for establishing two opposed limiting posit-ions to which it may be actuated with a snap motion when predetermined different temperatures obtain therein, said disk comprising a bimetallic memltier having an annular portion and a plurality of portions projecting radially inwardly therefrom, said plurality of portions being disconnected at their ends.

a. A thermostatic device comprising a bimetallic disk having spaced portions cut away between the periphery and the center thereof, the portions ren'iaining between the spaced portons bein severed from each other at the center or the disk.

In testimony whereof, I have hereunto subscribed my name this 25 day of January. 1927.

LEWIS .l'. GREENAl'VALT. 

